The present invention is directed to an apparatus for signalling the depletion of packaging film material at a pre-determined quantity level. More particularly, the present invention is directed to an apparatus and associated electrical circuitry for monitoring the amount of film left on the supply rolls so that an operator will be alerted to replenish the film supply before the film runs out as the product being packaged is being processed.
During a packaging operation in which product is advanced to a packing station along an endless conveyor belt, the use of packaging films and the amount remaining at a given time during the packaging operation is monitored so as to permit the operator to replenish the packaging material without the loss of goods being processed, due to insufficient packaging material. Obviously, a failure to have sufficient packaging material on hand can result in machine down-time and loss of product.
On packaging machines of the type known to the prior art as, for example, shown in U.S. Pat. No. 3,503,175, the film supplies are monitored by mercury switches disposed on counter balanced film sensing fingers. These sensing fingers are wired in series with the main motor drive control, with the result that if either top or bottom film supply is depleted, a mercury switch is caused to move and the machine is de-energized until the operator places a fresh roll of packaging material into the manufacturing line. Unfortunately, with the aforementioned type of system, the machine operator is unaware of film depletion until it actually occurs; that is, there is no warning and once such an occurrence takes place, the machine shuts off with the result that product to be packaged accumulates until the operator places a fresh supply of packaging material on stream and re-energizes the machine. With machines of this type, the rate at which product was handled was sufficiently low in some instances so as not to cause a serious problem at the time the packaging machine was de-energized due to a lack of packaging film. However, with an increase in the amount of product throughput and the resultant high speeds of operation, machine shutdown due to insufficient supplies of packaging material can be catastrophic, with the result that the operator had to hand feed loose and disorganized product into the production line so as to correct the aforementioned problem.